Man-Made Changes in the Freshwater Input Rates of Hudson and James Bays

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Author: Prinsenberg, S. J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1980
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Hudson; Rupert; Eastmain; Winter River; Churchill River; La Grande River; James Bay
• Online Access: http://dx.doi.org/10.1139/f80-143; http://www.nrcresearchpress.com/doi/pdf/10.1139/f80-143

The freshwater input rates of the Hudson/James Bay region were obtained on a monthly time scale and include contributions of evaporation, precipitation, and river runoff. The yearly mean precipitation minus evaporation rate shows that it behaves as an oceanic region supplying the overlying air mass with moisture. The monthly runoff rates for the total region and James Bay alone have minimum values during the winter and maximum values during the spring freshet. The total freshwater input can be divided into a winter and summer season. The large input of the summer represents an average monthly addition of a 10.0-cm layer of fresh water while the smaller winter input amounts to addition of a 0.5-cm layer of freshwater. Annually, the total surface area receives a layer of 64 cm of freshwater.During the 1980s, four hydroelectric developments will cause temporal changes in the freshwater input cycle as winter river runoff rates will increase to values comparable to spring peak runoffs. In the Nelson–Churchill River development, the Churchill River runoff will be reduced to 29% of its natural state during the winter and to 54% during the summer. This water will increase the runoff into the Nelson River Delta by 52% in the winter and 10% in the summer. Similarly, the Eastmain River runoff will be reduced by 79%. The La Grande River will double its yearly averaged runoff rate and experience a 500% increase in runoff during the winter. The other two developments, Nottaway–Broadback–Rupert rivers (N.B.R.) and Great Whale–Little Whale proposals, will experience similar changes: large increases in the winter runoff rates and small decreases in summer rates.The total freshwater input into James Bay will be doubled during the winter months. In addition, half the future input will occur in the northern region which now receives only 20%. The La Grande River winter runoff rate will equal in magnitude that of the Nelson River Delta which presently accounts for 25% of the Hudson/James Bay winter runoff. The runoff for the total ...